低压断路器中空气电弧重击穿现象的仿真与实验研究

Simulation and Experimental Research on Air Arc Restriking in Low-voltage Circuit Breaker

低压断路器用于接通和分断电路中的电流。当故障电流产生时,动触头和静触头打开,在触头间产生电弧,随后在电磁场和气流场的作用下向灭弧栅片运动。在运动过程中会出现电弧的停滞和后退的重击穿现象,严重降低了断路器的开断性能。该文以磁流体动力学(MHD)为基础建立了三维空气电弧等离子体在外部磁场作用下运动的数学模型,此模型可以预测电弧的重击穿现象,并发现当灭弧室的出口面积为60%时,电弧在3mT磁场的作用下运动时出现了重击穿现象,而当磁场增大到5mT时重击穿现象消失。此外,还发现当磁场为10mT时,在出口面积分别为20%、60%和100%3种情况下电弧均可以顺利到达栅片,在运动的过程中没有电弧重击穿现象的发生。

Low-voltage circuit breakers are used to switch on and off electrical current in circuit. During the interruption process, the contacts of the breaker are separated and an electric arc is established between contacts. Under the actions of Lorentz and aerodynamic forces, the arc has to move along the rail electrodes toward the quenching area. During the motion process, the stagnation and back commutation occur and worsen the performances of circuit breaker. According to the real interruption process, a three-dimensional（3-D） model of arc motion under the effect of external magnetic field is built based on magnetohydrodynamic（MHD）, which can predict the restriking phenomena. With air vents opened to 60%, the restriking phenomena occur under 3mT magnetic field; when the magnetic field is increased to 5mT, the restriking phenomena disappears. Moreover, it shows that with air vents opened to 20%, 60% and 100%, the arc can arrive in the splitter plates successfully under 10mT magnetic field without restriking.